Here we go! We're going to add 121 and 3319 together.

Step 1: We'll start by adding the digits 1 & 9 in column 1 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 2 & 1 in column 2 and get 4.

Step 3: We'll start by adding the digits 1 & 3 in column 3 and get 4.

Step 4: We'll start by adding the digits 0 & 3 in column 4 and get 3.

So, 121 + 3319 = 3440.

